1. Field of the Invention
This invention relates to a surface inspection method wherein a surface of a rubber or metal formed product is viewed by a television camera (video camera) and roughness or cracks of the specimen surface is inspected.
2. Description of the Prior Art
In conventional methods for inspecting roughness or cracks of surfaces of rubber or metal formed product, parallel rays passing through a thin slit are projected onto a surface of a specimen and the specimen surface is illuminated by parallel rays. Observation by visual inspection from the lateral side is carried out, whereby surface unevenness is determined from the contour of luminous lines visible on the surface. However, this method has disadvantages in that a demanding inspection technique is required in the visual inspection and the inspection work is time-consuming. Moreover, the method has disadvantages in that a luminous line formed by the projected rays becomes broad when inspecting a curved surface portion and that unequal brightness of parallel rays causes unequal brightness of the luminous line, resulting in reduction of accuracy of the inspection.